Chloroform is an organic compound with formula CHCl3. It is one of
the four chloromethanes. The colorless, sweet-smelling, dense liquid is a
trihalomethane, and is considered somewhat hazardous. Several million tons are
produced annually as a precursor to PTFE and refrigerants, but its use for
refrigerants is being phased out.
During prolonged storage in the presence of
oxygen, chloroform converts slowly to phosgene,
releasing HCl in the process. To prevent
accidents, commercial chloroform is stabilized with ethanol or amylene, but
samples that have been recovered or dried no longer contain any stabilizer.
Amylene has been found ineffective, and the phosgene can affect analytes in
samples, lipids, and nucleic acids dissolved in or extracted with chloroform.
Dissolved phosgene cannot be removed by distillation or carbon filters, but it
is removed by calcium hydroxide or
activated alumina. Phosgene and HCl can be removed from chloroform by
washing with saturated aqueous carbonate solutions, such as sodium bicarbonate.
This procedure is simple and results in harmless products. Phosgene reacts with
water to form carbon dioxide and HCl, and the carbonate salt neutralizes the
resulting acid. (Wikipedia)
To prepare chloroform easily, using acetone
and bleach to generate a haloform reaction may be a good method. The equation
and mechanism is shown below.
Reaction Equation
Mechanism
Chemicals
1.
Acetone: 36.1536 g
2.
12% sodium hypochlorite (or industrial
bleach): 1000.0 mL
3.
Magnesium sulfite anhydrous: Amount
Procedure
1.
Add 1000.0 mL filtered 12%
sodium hypochlorite in a serum bottle.[1]
2.
Chill the
bottle containing with 12% NaOCl(aq) in an ice bath.[2]
3.
Add 36.1536 g of
acetone into the bottle slowly.
4.
Stir the
mixture thoroughly and incubate on ice for 1~2 hours.
5.
Collect
the lower layer.
6.
Dry the
crude product with magnesium sulfate anhydrous.
7.
Distill
the dried product and collect the distillate at 61~62℃.
My fluid cooling system
8.
Dry the
product again with magnesium sulfate anhydrous.
9.
Figure
out the yield of chloroform.
10. Preserve the product in a brown glass bottle.
Notes
[1] There may have some
precipitate in the bottom of the bottle of industrial bleach. That is because sodium
hypochlorite may disproportionate at room temperature and produce sodium
chloride and sodium chlorate, and the solubility of sodium chloride is the
worst in these three salts. So the NaCl will salt out and form precipitate.
[2] Haloform reaction is an
exothermic reaction so the temperature of the mixture would raise high (about
70℃) if
cooling is not sufficient. High temperature may lead side reaction occur:
3
ClO-(aq) → ClO3-(aq) + 2 Cl-(aq)
This side reaction may reduce the
concentration of hypochlorite ion and cause decrease in the yield. So it is
important in controlling the temperature of the reactant.
Report Sheet
|
Volume of 12% sodium hypochlorite
|
1000.0 mL
|
|
Density of 12% sodium hypochlorite (24.0℃)
|
|
|
Test 1
|
1.1557 g/mL
|
|
Test 2
|
1.1618 g/mL
|
|
Average
|
1.1586 g/mL
|
|
Mole of sodium hypochlorite
|
1.8675 mol
|
|
Weight of acetone
|
36.1536 g
|
|
|
= 0.6225 mol
|
|
Theoretical weight of chloroform
|
74.2980 g
|
|
Weight of Chloroform
|
34.6337 g
|
|
Yield
|
46.61%
|
imma try this at home for research purposes
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